KR101878652B1 - Refining Method of Metal Using Integrated Electroreduction and Electrorefining process - Google Patents

Abstract

The present invention relates to a metal refining method, capable of producing a metal of high purity from a metal oxide by an environmentally friendly and safe method without requiring a chlorination process. The metal refining method according to the present invention includes: a step (a) of preparing, through electrolytic reduction using a solid metal cathode formed by using as a cathode, a metal that has an eutectic point of a first metal on a binary phase diagram, the first metal being a metal of a metal oxide, and has an eutectic point of a third metal on the binary phase diagram, the third metal being one or more metals selected from the group consisting of alkali metals and alkaline earth metals, an alloy of the first metal and a second metal that is a metal of the metal cathode; and a step (b) of electrolytically refining the alloy solidified and collecting the first metal from the alloy.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal refining method using an electrolytic reduction and an electrolytic refining continuous process,

The present invention relates to a metal refining method, and more particularly, to a metal refining method capable of producing a high-purity metal by using a metal oxide as a raw material in an environment-friendly and safe manner and producing a high quality metal having a significantly low oxygen content .

A typical process for the reduction of existing zirconium and titanium metal oxides is the Kroll process (US 5,035,404). The Kroll process is a process based on a chlorination process. Since magnesium is used to reduce zirconium chloride or titanium, the process is complicated and the probability of chlorine gas generation is high, which is an environmental problem. have. The electrolytic reduction process has been studied as a substitute for the existing crawl process. It has many merits such as the ability to maintain the shape of the precursor material and the advantage that chlorine gas is not generated. However, There is still a problem in that the oxygen concentration after the process is difficult to control since the metal is limited to some types such as titanium and tantalum and the recovered metal is limited to powder or porous form. An electrolytic reduction method using a molten oxide electrolyte has been reported as an approach to control a high oxygen concentration caused by a large surface area of such a product (Antoine Allanore, Journal of The Electrochemical Society, 162 (1) (2015) E13-E22) This process requires a high temperature of 1500 ° C or higher in order to melt the oxide raw material and has a limit to be applied to a high melting point metal having a melting point of 1700 ° C or higher like Ti and Zr. In order to overcome this problem, it is necessary to lower the specific surface area of the Ti and Zr target metals produced by the electrolytic reduction reaction in the electrolyte so as not to cause reoxidation. However, in the case of Ti and Zr, the reduction of specific surface area due to melting is practically impossible.

United States Patent 5,035,404

Antoine Allanore, Journal of The Electrochemical Society, 162 (1) (2015) E13-E22

 It is an object of the present invention to provide a metal refining method capable of producing a high purity metal from a metal oxide by an environmentally friendly and safe method that does not require a chlorination step will be.

It is another object of the present invention to provide a metal refining method capable of producing a high purity metal from a metal oxide in the atmosphere in an environmentally friendly and safe manner by eliminating a chlorination step.

It is still another object of the present invention to provide a metal refining method capable of producing a high quality metal having a remarkably low oxygen content from metal oxides.

Still another object of the present invention is to provide a metal refining method which is advantageous for commercialization because it is possible to perform a relatively low temperature process and has an energy efficient and simple process.

The metal refining process according to the present invention comprises the steps of: a) preparing a mixture of an alkali metal and an alkaline earth metal having a eutectic point and a first metal which is a metal of a binary metal oxide, Preparing an alloy between the first metal and a second metal, which is a metal of the metal cathode, through electrolytic reduction using a solid metal cathode having a metal and a metal having an eutectic point as a cathode; And b) an electrolytic refining step of electrolytically refining the solidified alloy, and recovering the first metal from the alloy.

In the metal refining method according to an embodiment of the present invention, the step a) includes the steps of: a1) electrolyzing the oxide of the third metal using an electrolyte containing an oxide of the third metal, Preparing a third metal and a second intermetallic alloy; And a2) introducing a metal oxide, which is an oxide of the first metal, into the electrolyte to convert an alloy between the third metal and the second metal into an alloy between the first metal and the second metal.

In the metal refining method according to an embodiment of the present invention, the third metal and the second intermetallic alloy may have a relatively higher density than the electrolyte.

In the metal refining method according to one embodiment of the present invention, the temperature in step a1) may satisfy the following relational expression (1).

(Relational expression 1)

Te < Ta1 &amp;le; 1.8Tm

In the relational expression 1, Ta1 is the temperature in the a1) step, Te is the eutectic temperature in binary states of the third metal and the second metal, and Tm is the melting temperature of the third metal.

In the metal refining method according to an embodiment of the present invention, the temperature in step a2) may satisfy the following relational expression (2).

(Relational expression 2)

Te < Ta2 &lt; 1.5Tm &

In the relation 2, Ta2 is the temperature of step a2), Te 'is the eutectic temperature of the binary state of the first metal and the second metal, and Tm' is the melting temperature of the second metal.

In the metal refining method according to an embodiment of the present invention, the metal oxide may satisfy the following formula (1).

(Formula 1)

M _x O _y

Wherein M is a first metal, a metal having a negative standard reduction potential with respect to a standard reduction potential of a second metal which is a metal of the metal cathode, x is a real number of 1 to 3, y is a real number of 1 to 5 to be.

In the metal refining method according to an embodiment of the present invention, the metal oxide may be selected from the group consisting of zirconium oxide, hafnium oxide, titanium oxide, tungsten oxide, iron oxide, nickel oxide, zinc oxide, cobalt oxide, manganese oxide, Gallium oxide, lead oxide, tin oxide, silver oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, promethium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium Wherein the metal oxide is selected from the group consisting of oxides, ytterbium oxides, actinium oxides, thorium oxides, protactinium oxides, uranium oxides, neptunium oxides, plutonium oxides, amerium oxides, cerium oxides, berkelium oxides, caliperum oxides, And a complex thereof.

In the metal refining method according to an embodiment of the present invention, the oxide of the third metal may be Li ₂ O, Na ₂ O, SrO, Cs ₂ O, K ₂ O, CaO, BaO, or a mixture thereof.

In the metal refining method according to an embodiment of the present invention, the electrolyte during the electrolytic reduction may be a molten salt, and the molten salt may be a molten salt of a halide of one or more metals selected from the group of alkali metals and alkaline earth metals .

In the metal refining method according to an embodiment of the present invention, the solidification of the alloy between the first metal and the second metal is slowly cooled at a cooling rate of 20 DEG C / min or lower from the temperature of the liquid metal cathode at the time of electrolytic reduction to room temperature Can be solidified.

In the metal refining method according to an embodiment of the present invention, the alloy between the first metal and the second metal may contain at least 2.1 wt% of the first metal.

In the metal refining method according to an embodiment of the present invention, the metal cathode may be copper.

The refining method according to the present invention is advantageous in that it is eco-friendly and excellent in stability because it does not need a chlorination step because it refines a metal (target metal) which is difficult to refine, such as zirconium, by an electrolytic reduction process.

Further, the refining method according to the present invention is a refining method using a solid metal cathode having a metal cathode and a process point and having a process point with a metal selected from the group of alkali and alkaline earth metals, After the alloy is prepared, the liquid precursor alloy is converted into an alloy between the metal of the metal cathode and the desired metal, whereby the refining can be performed in a state where the contact with the gas is originally shut off. And there is an advantage that a metal of high purity in which residual oxygen is remarkably reduced can be produced.

Further, the refining method according to the present invention uses a metal having a positive standard reduction potential higher than the standard reduction potential of the target metal as the metal of the metal cathode, and the reducing potential of the target metal Since the value is increased in the positive direction, there is an advantage that the reduction is performed more easily.

Further, the refining method according to the present invention is based on a two-phase region reaction in which a solid phase and a liquid phase coexist at a temperature relatively lower than the melting point of the two metal materials in a process state diagram, The present invention provides a metal refining method which is advantageous for commercialization because it can be processed at a relatively low temperature and has an energy efficient and simple process.

Further, the refining method according to the present invention is advantageous in that an alloy between a metal of a metal anode and a desired metal is solidified to electrolytically refine an alloy of a solid phase, and a metal having a high purity can be produced with improved efficiency.

Further, the refining method according to the present invention is a method of refining a metal anode by using a metal which forms a desired metal and an intermetallic compound, Alloy) can be stably and efficiently refined, and the refinement of a thick solid alloy is also possible.

1 is a process diagram showing an electrolytic reduction process in a metal refining method according to an embodiment of the present invention,
2 is a process diagram showing an electrolytic refining process in the metal refining method according to an embodiment of the present invention,
FIG. 3 is another process drawing showing the electrolytic reduction step in the metal refining method according to an embodiment of the present invention,
FIG. 4 is another process diagram showing a conversion step performed after the electrolytic reduction in the metal refining method according to an embodiment of the present invention,
5 is a scanning electron microscope (SEM) image of an alloy obtained in an electrolytic reduction process in an embodiment of the present invention,
6 is a scanning electron microscope (SEM) image of another alloy obtained in an electrolytic reduction process in an embodiment of the present invention,
7 is a scanning electron microscope (SEM) image of another alloy obtained in an electrolytic reduction process in an embodiment of the present invention,
8 is a scanning electron microscope (SEM) image of another alloy obtained in an electrolytic reduction process in an embodiment of the present invention,
9 is a graph showing the results of an X-ray diffraction test of an alloy obtained in an electrolytic reduction process in an embodiment of the present invention,
FIG. 10 is a graph showing an optical photograph, a scanning electron microscope photograph and an EDS element analysis result of an anode and a cathode observed in an electrolytic refining step in an embodiment of the present invention,
FIG. 11 is a scanning electron microscope (SEM) image of a cross section of an anode after an electrolytic refining process is performed in an embodiment of the present invention,
12 is a scanning electron microscope (SEM) image of a Cu-Zr alloy containing 1.21 wt% Cu.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a metal refining method of the present invention will be described in detail with reference to the accompanying drawings. The following drawings are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the following drawings, but may be embodied in other forms, and the following drawings may be exaggerated in order to clarify the spirit of the present invention. Hereinafter, the technical and scientific terms used herein will be understood by those skilled in the art without departing from the scope of the present invention. Descriptions of known functions and configurations that may be unnecessarily blurred are omitted.

The metal refining method according to the present invention is characterized in that the metal refining method comprises the steps of electrolytic reduction using a first metal which is a metal of a binary oxide metal oxide and a metal cathode which has an eutectic point, An electrolytic reduction step of producing an alloy between metals; And electrolytically refining the solidified alloy to recover the first metal from the alloy.

The metal refining method according to the present invention can be embodied in the first aspect using a liquid metal cathode and the second aspect using a solid metal cathode according to the phase of the metal cathode during electrolytic reduction.

The first aspect is a mode in which an alloy between a first metal (a metal of a metal oxide, a target metal to be refined) and a second metal (metal of the metal cathode) is produced as a product of an electrolytic reduction process using a liquid metal cathode have.

The second aspect can be an aspect in which an alloy of a liquid, which is an intermediate product, is converted into an alloy between the first metal and the second metal after the solid metal cathode is used to produce an alloy of liquid as an intermediate product as a product of electrolytic reduction .

The second aspect is a method for physically separating a continuous multistage reaction occurring when an electrolyte of an electrolytic reduction process in an embodiment of the first embodiment further contains an oxide of a metal selected from the group consisting of alkali metals and alkaline earth metals, And it is possible to develop it to enable an atmospheric process (atmospheric refining process).

Hereinafter, the metal refining method according to the first aspect will be described in detail.

In the metal refining method according to the present invention, the metal anode is a liquid metal cathode, and the metal oxide is electrolytically reduced to produce an alloy between the liquid first metal and the second metal. That is, the metal refining method according to the present invention comprises the steps of electrolytically reducing a raw material containing the metal oxide by using a first metal which is a metal of a binary oxide state metal oxide and a metal anode which has an eutectic point, An electrolytic reduction step of producing an alloy between a metal and a second metal which is a metal of the liquid metal cathode; And electrolytically refining the solidified alloy to recover the first metal from the alloy. A binary state of the second metal as the metal cathode and an eutectic point as the binary state of the first metal cause the metal oxide (the oxide of the first metal) to undergo electrolytic reduction, the alloy between the first metal and the second metal Can be produced.

As described above, the metal refining method according to the present invention is a method of refining a raw material containing a metal oxide by electrolytically reducing the metal oxide, and a liquid metal cathode is subjected to an eutectic phase with a target metal (a first metal which is a metal of a metal oxide) The metal (metal) of the metal oxide (the first metal) is electrolytically reduced and the melting point of the metal (the first metal) is lowered by the eutectic reaction, so that the electrolytic reduction can be effectively performed at a relatively low temperature, , The reduction metal (first metal) is obtained in the form of a liquid alloy (an alloy of the first metal and the second metal) by the process reaction, so that contamination by oxygen can be remarkably prevented.

Further, even if the metal oxide contained in the raw material is a substance which is difficult to be electrolytically reduced by the metal, the difference between the standard redox potential difference between the second metal which is the metal of the liquid metal cathode and the first metal, There is an advantage that the metal oxide can be easily reduced. That is, when a metal having a positive standard reduction potential than the standard reduction potential of the first metal is used as the metal of the liquid metal negative electrode, the standard reduction potential value of the first metal is shifted in the positive direction by the liquid metal negative electrode The electrolytic reduction of the metal can be made easier.

Further, the metal refining method of the present invention is a refining method of a metal according to the present invention, in which a liquid alloy obtained by electrolytic reduction is solidified and then a solid alloy is electrolytically refined to obtain a desired metal, (Productivity) can be greatly improved, which is advantageous for commercialization. In addition, electrolytic refining is performed in the form of an ingot having a good conductivity by solidifying a liquid-phase alloy, so electrolytic refining can be effectively and easily performed without any other pretreatment other than the shape processing. Particularly, when electrolytic refining is performed by solidification, it is advantageous in terms of efficiency because it is easy to raise the reaction area during refining.

In the metal refining method according to an embodiment of the present invention, the metal oxide contained in the raw material may satisfy the following chemical formula (1).

(Formula 1)

M _x O _y

Wherein M is a metal which is a metal to be reduced and is a metal having a negative standard reduction potential with respect to a standard reduction potential of a second metal which is a metal of the liquid metal cathode, x is a real number of 1 to 3, y is It is a real number from 1 to 5.

The metal oxide according to Formula 1 is an oxide of the first metal having a negative standard reduction potential that is lower than the standard reduction potential of the second metal that is the metal of the liquid metal cathode, Even if the standard reduction potential value is increased in the positive direction, even if the metal oxide is difficult to electrolytically reduce, it can be easily reduced to a metal.

As a specific example, the metal oxide may be at least one selected from the group consisting of zirconium oxide, hafnium oxide, titanium oxide, tungsten oxide, iron oxide, nickel oxide, zinc oxide, cobalt oxide, manganese oxide, chromium oxide, tantalum oxide, gallium oxide, Wherein the metal oxide is selected from the group consisting of oxides, lanthanum oxides, cerium oxides, praseodymium oxides, neodymium oxides, promethium oxides, samarium oxides, europium oxides, gadolinium oxides, terbium oxides, dysprosium oxides, holmium oxides, erbium oxides, thulium oxides, , Plutonium oxide, uranium oxide, neptunium oxide, plutonium oxide, amerium oxide, cerium oxide, berkelium oxide, caliperum oxide, euinitanium oxide, ferric oxide, mandelverium oxide, Two or more of them may be selected, but the present invention is not limited by the kind of the metal oxide.

In other words, the metal refining method according to an embodiment of the present invention includes the steps of: selecting a metal (first metal) to be refined; Selecting a metal (second metal) of a metal cathode (having a binary eutectic melting point) forming a eutectic phase with a selected metal (first metal); And electrolytically reducing a raw material containing an oxide of the metal selected using the selected metal cathode in a liquid state.

The step of selecting the second metal further includes the step of forming a eutectic phase with the first metal and forming an eutectic phase with a standard reduction of the first metal to a standard reduction potential of the first metal based on the standard reduction potential of the first metal, And selecting the metal having the dislocation as the metal (second metal) of the liquid metal cathode.

The liquid metal cathode can be used as long as it meets the above-described eutectic phase forming conditions and conditions that have a standard reduction potential higher than the standard reduction potential of the first metal. However, in order to have a process temperature as low as possible with the eutectic phase formation, it is advantageous that the second metal satisfies the above-mentioned conditions and has a low melting point.

Further, in the metal refining method according to an embodiment of the present invention, after the electrolytic reduction is performed, the liquid alloy of the first metal and the second metal obtained in the electrolytic reduction process is solidified, and electrolytic refining of the solidified alloy is performed do. Accordingly, it is advantageous that the second metal, which is the metal of the liquid metal cathode, is a metal that does not solubilize the first metal as much as possible and that forms an intermetallic compound with the first metal. This is because when the second metal forms a solid solution with the first metal or when the solubility limit of the first metal is high, the diffusion rate of the first metal from the center of the solidified alloy to the surface The speed of electrolytic refining is determined by the electrolytic refining process, and the electrolytic refining efficiency is significantly lowered.

Accordingly, the step of selecting the second metal may include forming a eutectic phase with the first metal, and performing a standard reduction of the first metal relative to the standard reduction potential of the first metal based on the standard reduction potential of the first metal. And a metal having a dislocation and forming an intermetallic compound with the first metal as a metal (second metal) of the liquid metal cathode.

As a specific example, the metal (second metal) of the liquid metal cathode may be selected from one or more of Cu, Sn, Zn, Pb, Bi, Cd and their alloys, It is not. Here, the second metal may be a different kind of metal than the first metal.

As described above, the refining method according to an embodiment of the present invention is advantageous in that it can minimize the contamination of oxygen (oxygen impurities) and also reduce the metal oxide which is difficult to electrolytically reduce at a relatively low processing temperature. With these advantages, the refining process according to the present invention is particularly advantageous in replacing the method of making zirconium or titanium based on the conventional crawling process. That is, the refining method according to one embodiment of the present invention may be a refining method of zirconium or titanium, and may be replaced with a commercial crawling process, and refining of zirconium or titanium that can minimize contamination with oxygen Lt; / RTI &gt;

When the desired metal is zirconium or titanium, the liquid metal cathode forms a eutectic phase with zirconium (or titanium) and has a positive standard reduction potential greater than the standard reduction potential of zirconium (or titanium) And may be a metal forming an intermetallic compound. When the target metal is zirconium or titanium, copper is one example of a specific liquid metal cathode. Copper is substantially free of zirconium (or titanium), and in a wide variety of compositions, zirconium (or titanium) and intermetallic compound Which is advantageous. In addition, copper can facilitate the electrolytic reduction reaction of zirconium oxide (or titanium oxide), which has a difference in standard reduction potential from zirconium (or titanium), which is difficult to electrolytically reduce. Furthermore, as described above, not only can the contamination with oxygen be prevented by the eutectic phase using the liquid metal cathode, but also when the liquid metal cathode is made of copper, the amount of dissolved oxygen in the copper is very low and the alloy and / It is possible to remarkably reduce the oxygen content of the metal. As a specific example, when the target metal is zirconium or titanium, the oxygen content of the metal obtained by alloying and / or electrolytic refining can be controlled to less than 1000 ppm by using the liquid metal cathode as copper

1 is a process diagram showing an electrolytic reduction step in a refining method according to an embodiment of the present invention. 1, the electrolytic reduction includes a liquid metal cathode (molten metal in FIG. 1), an electrolyte (molten salt in FIG. 1), and an anode (anode in FIG. 1) and a reference electrode Lt; / RTI &gt; During electrolytic reduction, a raw material containing a metal oxide is contained in the electrolyte and an electrolytic reduction process can be performed. At this time, the metal oxide may be in powder form, and it is advantageous that the average particle size is 100 μm or less, specifically 1 μm to 20 μm so as to be stably dispersed in the electrolyte.

The electrolyte in the electrolytic reduction step may be a molten salt in which the halide of one or more selected metals in the alkali metal and alkaline earth metal groups is melted. More specifically, the electrolyte in the electrolytic reduction step is a halide of one or more metals selected from the group consisting of alkali metals including Li, Na, K, Rb and Cs and alkaline earth metals including Mg, Ca, Sr and Ba May be a molten molten salt. Wherein the halide may comprise chloride, fluoride, bromide, iodide or mixtures thereof. It is preferable to use a salt having a higher boiling point of the electrolyte so that the metal used as the cathode is melted (liquid-phase negative electrode). In this respect, it is advantageous that the electrolyte in the electrolytic reduction process is chloride, and calcium chloride (CaCl ₂ ) is more advantageous.

The electrolyte in the electrolytic reduction step may further comprise an additive which is an oxide of one or more metals selected from the group consisting of alkali metals and alkaline earth metals. The content of the additive may be 0.1 to 25% by weight based on the total weight of the electrolyte. As a specific example, the oxides of the metal selected from the group of alkali metals and alkaline earth metals may include Li ₂ O, Na ₂ O, SrO, Cs ₂ O, K ₂ O, CaO, BaO, have. The oxide of the metal contained in the electrolyte is advantageous because it enables easier reduction of the metal oxide contained in the raw material.

For example, when the metal to be produced is zirconium, the raw material contains zirconium oxide, the liquid metal cathode is copper, and the electrolyte does not contain any of the additives described above, When the electrolyte contains the above-mentioned additive, the indirect reduction reaction, which is a reaction selected from one or more of the following Reaction Schemes 2 to 4, is possible, so that the metal oxide can be more effectively reduced at a lower cathode potential.

(Scheme 1)

ZrO ₂ + Cu + 4e ^- -> CuZr + 2O ^{2 -}

At this time, the product oxygen ion after the reaction can be converted into CO ₂ , CO or O ₂ depending on the anode used.

(Scheme 2)

ZrO ₂ + CaO - > ZrCaO ₃

ZrCaO ₃ + Cu + 4e ^- - > CuZr + CaO + 2O ^2-

In the reaction of the reaction formula (2), the compound is formed by the reaction of the electrolyte additive and the zirconium oxide in the first stage by the reaction of the two stages, and then the compound is electrolytically reduced at the second stage to produce the copper-zirconium alloy.

(Formula 3)

Ca ²⁺ + 2e ^- - > Ca

_{2Ca + ZrO 2 + Cu ->} CuZr + 2CaO

The reaction of Scheme 3 is a two-step reaction in which calcium ion is reduced to calcium in the first stage and calcium produced in the second stage is chemically reacted with the zirconium oxide to form a zirconium metal. As the reaction occurs in the liquid copper cathode, Finally, a copper-zirconium alloy can be formed.

(Scheme 4)

ZrO ₂ + CaO - > ZrCaO ₃

Ca ²⁺ + 2e ^- - > Ca

_{3Ca + CaZrO 3 + Cu ->} CuZr + 3CaO

The reaction of Reaction Scheme 4 is a three-step reaction. In Step 1, an electrolyte additive and zirconium oxide react to form a compound. In Step 2, calcium ions are reduced to calcium through an electrolytic reduction process. A zirconium metal can be produced. At this time, as the electrolytic reduction process and the chemical reduction process occur in the liquid copper cathode, the copper-zirconium alloy can be finally produced by reacting with metal zirconium and liquid metal copper.

The current density at the electrolytic reduction step is sufficient for a current density capable of stable electrolytic reduction. As a specific example, the current density at the electrolytic reduction step may be 100 to 1000 mA / cm ² , more specifically 300 to 700 mA / cm ² , but is not limited thereto. The time during which the electrolytic reduction step is performed may be the time for which all the metal oxides are reduced. For example, the electrolytic reduction step may be performed for 30 minutes to 8 hours, but the time during which the electrolytic reduction is performed may be appropriately controlled in consideration of the amount of the metal oxide to be added, It is needless to say that it can not be limited by time. In addition, the potential applied to the negative electrode during the electrolytic reduction step may be such that a stable reduction reaction can occur. As a specific example, the potential applied to the cathode may be -0.3 to -4 V relative to the hydrogen reduction potential, but is not limited thereto.

An anode or a reference electrode can be used if it is a positive electrode or a reference electrode conventionally used for electrolytic reduction of a metal oxide. As a specific and non-limiting example, graphite or the like may be used as the anode, and W (pesudo) or the like may be used as the reference electrode, but it goes without saying that the present invention can not be limited by the anode or the reference electrode material.

The process temperature of the electrolytic reduction process may be a temperature above the melting point of the electrolyte and the melting point of the liquid metal cathode. However, in terms of preventing excessive energy consumption while maintaining a stable molten phase, the temperature difference between the melting point of the electrolyte and the melting point of the metal material of the liquid metal cathode, which is relatively higher than the melting point, is 10 to 200 ° C good. As a practical example, if the electrolyte is CaCl ₂ molten salt and the metal used as the cathode is copper, the process temperature at which electrolytic reduction is performed may be from 1100 ° C to 1200 ° C.

In the refining process according to an embodiment of the present invention, the alloy (liquid alloy) obtained by electrolytic reduction preferably contains 2.1% by weight or more of the first metal, more preferably 7% by weight, It is preferable to contain at least 16% by weight of the first metal.

As described above, when the electrolytic reduction step is completed after the electrolytic reduction step, the liquid metal cathode is converted to the liquid alloy. Thereafter, as the liquid alloy solidifies and the solid alloy is electrolytically refined, when the first metal contained in the liquid alloy is 2.1% by weight or less, a continuous mass transfer path of the first metal in the solid alloy is not formed, There is a risk that it will not be done. In detail, as the liquid alloy solidifies, the solid phase alloy has a microstructure structure in which a phase of the first metal, which is the metal of the liquid metal cathode, and a phase of the intermetallic compound of the first metal and the second metal coexist (microstructure). When the content of the second metal contained in the alloy is 2.1 wt% or less, the structure of the solid-state alloy is such that the intermetallic compound of the first metal and the second metal forms a matrix of the first metal in an island- Or the like. In such a case, the second metal is trapped in the matrix during the electrolytic refining of the solid-phase alloy, so that it is difficult to escape out of the solid-state alloy.

Thus, the liquid alloy contains at least 2.1 wt% of the first metal, and in the structure structure of the solid phase alloy, intermetallic compound phases of the first metal and the second metal are continuously connected to each other, It is necessary to provide a material movement path of the metal so that the electrolytic refining can be performed.

Specifically, the liquid alloy may contain at least 2.1 wt.% Of the intermetallic compound of the first metal and the second metal such that the intermetallic compound of the first metal and the triple point of the first metal grain can stably form a continuum. The first metal is preferably contained, more preferably, at least 7 wt% of the first metal.

The intermetallic compound grains of the first metal and the second metal themselves can stably form an intermetallic compound in a continuous manner (for example, without interposing a first metal grain, a triple point, etc.) continuum, the liquid alloy preferably contains at least 16% by weight of the first metal. At this time, the upper limit of the first metal content in the substantial liquid alloy may be 70% by weight.

At this time, the first metal content in the alloy can be controlled by controlling the mass of the liquid metal cathode and the metal oxide charged into the electrolyte during the electrolytic reduction, and independently controlling the time during which the electrolytic reduction is performed . As a specific example, the metal oxide is reduced in the liquid metal cathode during electrolytic reduction, and as the liquid metal cathode is converted into the alloy, the metal oxide to be charged into the electrolyte during the electrolytic reduction is converted into the metal (first metal) (First metal) of the metal oxide is 2.1% by weight or more, preferably 7% by weight or more preferably 16% by weight or more based on the total weight of the metal (second metal) Or more, so that the first metal content in the alloy can be controlled. Alternatively, the first metal content in the alloy can be controlled by controlling the time during which electrolytic reduction is performed after a certain amount of metal oxide is input to the electrolyte.

After the electrolytic reduction is completed, cooling for solidification of the liquid alloy can be performed. At this time, since the first metal and the second metal are homogeneously mixed in the liquid alloy, the structure of the alloy obtained after solidification by the cooling rate of the liquid alloy is greatly influenced. The cooling rate can be controlled by controlling the temperature of the liquid metal cathode (electrolysis) so that an intermetallic compound phase can be stably formed and a structure of intermetallic compound phases of the first metal and the second metal are continuously connected to each other. Cooling process temperature) to room temperature and a cooling rate of 20 DEG C / min or less. If the cooling rate is excessively fast out of the range suggested, an intermetallic compound may not be formed or a structure in which fine intermetallic compound particles are embedded in the first metal matrix in a large amount may be obtained, and a continuous and fast first metal substance There is a risk that the movement path can not be formed. At this time, if the cooling of the liquid metal cathode is excessively slow, the advantages on the microstructure are negligible, but as the time required for the process becomes excessively long, the cooling rate is substantially 1 DEG C / min or more, more practically 5 DEG C / min Or more.

However, the present invention is not limited to solidification by direct slow cooling of the liquid alloy obtained by electrolytic reduction. As a specific example, the liquid alloy obtained by electrolytic reduction is solidified, and then the alloy is cast into a designed shape suitable for electrolytic refining through molding and heat treatment using powder of solidified alloy or casting using a melt (reflow) of solidified alloy And cooling may be performed at a cooling rate of 20 DEG C / min or less in this forming step. That is, the above-described slow cooling may be performed at the stage of producing a solid phase alloy used for electrolytic refining.

After the electrolytic reduction step described above, an electrolytic refining step may be performed in which the alloy is solidified to obtain a solid-phase alloy, electrolytically refining the solid-phase alloy, and recovering the first metal from the alloy. At this time, a step of removing the remaining electrolyte from the product obtained in the electrolytic reduction step may be further performed before the electrolytic refining of the product (solidified alloy) obtained in the electrolytic reduction step. The residual electrolyte removal step may include a step of subjecting the product obtained in the electrolytic reduction step to heat treatment in a vacuum or an inert gas atmosphere to distill off the electrolyte. The distillation temperature (heat treatment temperature) should be at least the melting point of the electrolyte used in the electrolytic reduction step. As a specific example, the distillation temperature may be 780 to 900 ° C, but is not limited thereto. In order to more effectively prevent the product obtained in the electrolytic reduction step from being oxidized again, it is preferable to use an inert gas to facilitate the distillation process in a vacuum atmosphere. The residual electrolyte removal process is a process in which the product (solidified alloy) obtained in the electrolytic reduction step is carried out in the solid phase state, so that the cooling rate is not particularly controlled in the case of performing the residual electrolyte removal process on the product obtained by the above- You do not have to.

2 is a process diagram showing a process of electrolytic refining in the refining method according to an embodiment of the present invention. As shown in Fig. 2, the electrolytic refining is performed in the same manner as in Example 1 except that the anode (anode of Fig. 1), the electrolyte (the molten salt of Fig. 2) and the cathode 2 &lt; / RTI &gt; reference electrode).

The electrolyte during electrolytic refining may be a molten salt in which a halide of one or more metals selected from the group of alkali metals and alkaline earth metals is melted independently of the electrolyte in the above electrolytic reduction step. More specifically, the electrolyte of the electrolytic refining process is a mixture of an alkali metal containing Li, Na, K, Rb and Cs and a halide of one or more metals selected from the group of alkaline earth metals including Mg, Ca, Sr and Ba May be a molten molten salt. Wherein the halide may comprise chloride, fluoride, bromide, iodide or mixtures thereof.

In order to lower the electrolytic refining process temperature, one or more of the electrolytes of the electrolytic refining process may be selected from LiCl, KCl, SrCl ₂ , CsCl, NaCl, LiF, KF, SrF ₂ , CsF, CaF ₂ and NaF . At this time, two or more salts may form a eutectic salt. More specifically, the electrolyte in the electrolytic refining process may comprise lithium halide and sodium halide, and more specifically, the electrolyte in the electrolytic refining process may comprise lithium fluoride and potassium fluoride. The temperature of the electrolytic refining step may be equal to or higher than the melting temperature of the electrolytic refining step. As a specific example, the temperature of the electrolytic refining process may be 600 to 800 ° C, but is not limited thereto. At this time, the electrolyte of the electrolytic refining process may further include an additive such as zirconium fluoride (ZrF ₄ ), and the additive may be contained in an amount of 1 to 10 wt% based on the total weight of the electrolyte.

The current density at the electrolytic refining step may be a current density at which stable electrodeposition of the first metal can occur. As a specific example, the current density at the electrolytic refining step may be 10 to 500 mA / cm ² , more specifically 50 to 200 mA / cm ² , but is not limited thereto. The time at which the electrolytic refining step is performed is not particularly limited, but may be performed for 1 to 20 hours.

The cathode or the reference electrode can be used as a cathode or a reference electrode which is commonly used for electrolytic refining of a metal. For example, stainless steel or the like may be used as the cathode and W (pesudo) or the like may be used as the reference electrode. However, it is needless to say that the present invention can not be limited by the cathode or the reference electrode material.

Hereinafter, the metal refining method according to the second aspect will be described in detail.

In the metal refining method according to the present invention, the metal cathode (second metal) is a solid metal cathode, the second metal is a binary metal, and the third metal is a metal selected from the group consisting of alkali metals and alkaline earth metals, May be a metal having an eutectic point.

That is, the metal refining method according to the present invention is a metal refining method having a eutectic point with a first metal which is a metal of a binary-phase metal oxide, and a metal selected from the group consisting of alkali metals and alkaline earth metals An alloy between the first metal and a second metal, which is a metal of the solid metal cathode, is produced through electrolytic reduction using a solid metal cathode having a third metal and a metal having a eutectic point as a cathode step; And b) an electrolytic refining step of electrolytically refining the solidified alloy, and recovering the first metal from the alloy.

Specifically, a metal refining method according to an embodiment of the present invention includes the steps of using an electrolyte containing an oxide of a third metal, which is one or more metals selected from the group consisting of alkali metals and alkaline earth metals, To produce a third metal and a second intermetallic alloy in a liquid state; a2) introducing a metal oxide, which is an oxide of the first metal, into the electrolyte to convert an alloy between the third metal and the second metal to an alloy between the first metal and the second metal; And b) an electrolytic refining step of electrolytically refining the alloy between the solidified first metal and the second metal to recover the first metal from the alloy between the first metal and the second metal. At this time, the electrolyte may be a molten salt electrolyte. Thus, step a1) comprises: a molten salt electrolyte containing an oxide of a third metal and a solid metal having a first metal and a process point in a binary state diagram and having a third metal and a metal having a process point in a binary state, And a step of electrolytically reducing the oxide of the second metal using a cathode to produce a third metal and a second metal alloy in a liquid state.

In the metal refining method according to an embodiment of the present invention, the third metal and the second intermetallic alloy may have a relatively higher density than the electrolyte. That is, the third metal and the second intermetallic alloy in step a1) have a relatively larger density than the molten salt electrolyte, and the oxide of the third metal is electrolytically reduced in the step a1), so that the third metal contacts the surface of the solid metal cathode The third metal and the second intermetallic alloy in the liquid state generated by electrodeposition on the molten salt electrolyte may sink to the bottom of the molten salt electrolyte rather than floating on the surface of the molten salt electrolyte. The third metal and the second intermetallic alloy in the liquid state sink to the bottom of the electrolytic reduction vessel where the electrolytic reduction occurs, and the third metal and the second intermetallic alloy in the liquid state are mixed with the first metal in a liquid state As the alloy is converted into the second intermetallic alloy, contact with the atmosphere in the entire process can be fundamentally cut off.

In the refining method of the first aspect described above, when the electrolyte further contains an additive which is an oxide of a metal (a third metal) selected from the group of alkali metals and alkaline earth metals, a lower cathode The reduction of the desired metal oxide can be effected more efficiently at the dislocation. This indirect reduction process should precede the reduction of the oxides of the third metal, but the reaction intermediates including the metals belonging to the alkali metal and alkaline earth metal groups (the third metal) are less dense than the electrolytes used in the electrolytic reduction process It can rise like sludge. The floating metal (third metal) is brought into contact with the atmosphere gas. If the atmosphere gas contains oxygen such as atmospheric air, the floating reaction intermediate products are oxidized again and the reduction efficiency may be lowered. Thus, in the first embodiment, when the electrolyte contains an oxide of the third metal as an additive, there is a limitation that electrolytic reduction must be performed in a protective atmosphere containing no oxygen.

However, the method according to the embodiment of the present invention using the solid metal cathode can be performed in the air as the contact with the gas is essentially blocked in the electrolytic reduction process. Further, a liquid alloy which is an intermediate in the solid metal cathode state is obtained in a state in which the contact with the atmosphere is blocked, and the liquid alloy as the intermediate is still in contact with the atmosphere and the desired first metal- , The content of oxygen (dissolved oxygen) of the alloy obtained with respect to the one embodiment can be further lowered.

As described above, the second embodiment can perform the atmospheric electrolytic reduction process while maintaining the advantage according to the first aspect, and can have a high reduction efficiency at a lower energy condition than the first embodiment.

FIG. 3 is a process diagram illustrating a process in which electrolytic reduction is performed in a refining method according to an embodiment of the present invention.

As shown in Fig. 3, the electrolytic reduction is carried out using a solid metal cathode (cathode, M2 in Fig. 3), an electrolyte (molten salt in Fig. 3) and an anode (anode in Fig. 3) and a reference electrode In an electrolytic reducing bath. In the electrolytic reduction, the electrolyte contains an oxide (M3 of FIG. 3) of a metal (a third metal) belonging to the alkali metal and alkaline earth metal group, but does not contain a metal oxide (an oxide of the first metal) have.

Accordingly, the oxide of the third metal is reduced during the electrolytic reduction, and the third metal (M3 in FIG. 3) can be electrodeposited on the surface of the solid metal cathode. As the metal cathode material has an eutectic point with the third metal in the binary state, the third metal that is electroplated on the metal cathode surface reacts with the solid metal cathode, A second intermetallic alloy (M2M3 liquid droplet in Fig. 3) may be produced.

The generated liquid of the third metal and the second intermetallic alloy is higher in density than the electrolyte used in the electrolytic reduction process and can settle to the bottom of the electrolytic reduction tank. As the droplet of the alloy (the third metal and the second metal alloy), which sinks to the bottom of the electrolytic reduction bath, is brought into contact with the atmosphere gas in the electrolytic reduction process, the third metal is electroplated on the surface of the solid metal cathode, . That is, the contact between the intermediate product (the third metal, M3) or the product (M2M3 liquid) generated in the electrolytic reduction process and the oxygen in the atmosphere may be intrinsically blocked. Accordingly, the electrolytic reduction process can be performed in the atmosphere.

In the electrolytic refining process according to an embodiment of the present invention, the oxide of the metal (third metal) selected from one or more of alkali metals and alkaline earth metals contained in the electrolyte during the electrolytic reduction of FIG. 3 is Li ₂ O , Na ₂ O, SrO, Cs ₂ O, K ₂ O, CaO, BaO, or mixtures thereof. Advantageously, the oxides of the third metal preferably contain CaO which produces a third metal and a second intermetallic alloy with high density while providing a strong reducing power, and which can be subjected to an electrolytic reduction process at relatively low temperatures. At this time, the electrolyte may contain oxides of the third metal in an amount of 0.1 to 25% by weight based on the total weight of the electrolyte, but is not limited thereto.

In the electrolytic refining process according to an embodiment of the present invention, the electrolyte in the electrolytic reduction process of FIG. 3 may be a molten salt in which a halide of one or more metals selected from the group of alkali metals and alkaline earth metals is melted. More specifically, the electrolyte in the electrolytic reduction step is a halide of one or more metals selected from the group consisting of alkali metals including Li, Na, K, Rb and Cs and alkaline earth metals including Mg, Ca, Sr and Ba May be a molten molten salt. Wherein the halide may comprise chloride, fluoride, bromide, iodide or mixtures thereof. It is advantageous that the electrolyte in the electrolytic reduction process is a chloride in view of being able to be separated from the third metal and the second metal alloy (liquid phase) due to the high boiling point and stable at the process temperature and stably by the difference in density, and calcium chloride ₂ ) is more advantageous.

The metal cathode has a binary state eutectic point of the second metal to a third metal and at the same time satisfies the condition of having an eutectic point on the binary state of the first metal and the second metal, And a metal which does not belong to an alkaline earth metal can be used, and it is advantageous that the metal further satisfies the condition of having a standard reduction potential higher than the standard reduction potential of the first metal.

Further, in the metal refining method according to an embodiment of the present invention, the liquid alloy of the first metal and the second metal produced in the conversion step of a2) is solidified and electrolytic refining of the solidified alloy is performed. Accordingly, it is advantageous that the second metal, which is the metal of the liquid metal cathode, is a metal that does not solubilize the first metal as much as possible and forms an intermetallic compound with the first metal. This is because when the second metal forms a solid solution with the first metal or when the solubility limit of the first metal is high, the diffusion rate of the first metal from the center of the solidified alloy to the surface The speed of electrolytic refining is determined by the electrolytic refining process, and the electrolytic refining efficiency is significantly lowered.

Thus, the second metal forms an eutectic point with the third metal in the binary state, forms a eutectic point with the first metal in the binary state, and the standard reduction potential of the first metal Is a metal having a positive standard reduction potential relative to the standard reduction potential of the first metal and forming an intermetallic compound with the first metal. In the case of forming an intermetallic compound with the first metal, the first metal and the second metal may be eutectic at least between the second metal and the intermetallic compound between the first metal and the second metal, point can be located.

 As a specific example, the metal (second metal) of the liquid metal cathode may be selected from one or more of Cu, Sn, Zn, Pb, Bi, Cd and their alloys, It is not. The second metal is different from the first metal and is a metal selected from Cu, Sn, Zn, Pb, Bi, Cd, and alloys thereof.

As described above, the refining method according to the embodiment of the present invention can minimize the contamination (oxygen impurity) to oxygen as in the first embodiment, and the electrolytic reduction is performed at a relatively lower temperature than the first embodiment There is an advantage in that atmospheric refining can be performed. The refining process according to the present invention is particularly advantageous for replacing the conventional production process of zirconium or titanium based on the crawling process. That is, the refining method according to one embodiment of the present invention may be a refining method of zirconium or titanium, which can replace the conventional crawling process, can be commercialized, can minimize contamination with oxygen, Zirconium or titanium refining process.

When the target metal is zirconium or titanium, the metal cathode has a state of equilibrium with zirconium (or titanium) and has a standard reduction potential greater than the standard reduction potential of zirconium (or titanium) And a metal forming an intermetallic compound. When the target metal is zirconium or titanium, copper is one example of a specific metal cathode. Copper is substantially free of zirconium (or titanium), and in a wide variety of compositions, zirconium (or titanium) and intermetallic compounds . Further, in the process of converting the alloy between the second metal and the third metal into the alloy of the first metal and the second metal, the third metal has a very strong reducing power, while the copper has a standard reduction potential with zirconium (or titanium) It is possible to make the reduction reaction of the zirconium oxide (or titanium oxide) by the third metal to proceed more easily.

In the electrolytic refining step according to an embodiment of the present invention, the temperature at the time of electrolytic reduction in FIG. 3 may satisfy the following relational expression (1).

(Relational expression 1)

Te < Ta1 &amp;le; 1.8Tm

In the relation 1, Ta1 is the temperature (° C) of step a1), Te is the eutectic temperature (° C) in binary states of the third metal and the second metal, Tm is the melting temperature of the third metal (° C). If the binary state diagram of the third metal and the second metal has two or more process points, the Te of relational expression 1 may be a relatively low temperature among the process temperatures of two or more process points.

The temperature of the relational expression 1 is such that the metal cathode maintains the solid phase during the electrolytic reduction and the third metal and the second metal alloy in the liquid phase can be formed by the process reaction between the third metal and the solid metal cathode electrodeposited on the solid metal cathode Is the temperature. Advantageously, Ta1 in relation 1 can be Te < Ta1 &amp;le; 1.4Tm, more advantageously Te &lt; Ta1 &amp;le; 1.3Tm. At this time, it is needless to say that Ta1 satisfies the relational expression 1 and Ta1 is lower than the melting temperature of the metal cathode, as the metal cathode must maintain a solid state.

As a practical example, according to an advantageous example, when the third metal comprises CaO, the temperature during the electrolytic reduction of FIG. 3 may be from 750 to 1100 ° C, advantageously from 800 to 900 ° C.

The current density at the electrolytic reduction step is sufficient for a current density capable of stable electrolytic reduction. Examples specific one, and the current density during the electrolytic reduction step is 1 to 1000mA / cm ^2, may be a more specific range of 200 to 600mA / cm ^2, but is not limited to such. It is needless to say that the time during which the electrolytic reduction is performed can be appropriately adjusted in consideration of the amount of the third metal oxide to be added, and it is needless to say that the present invention can not be limited by the electrolytic reduction process time. In addition, the potential applied to the negative electrode during the electrolytic reduction step may be such that a stable reduction reaction can occur. As a specific example, the potential applied to the cathode may be -0.3 to -4 V relative to the hydrogen reduction potential, but is not limited thereto. An anode or a reference electrode can be used if it is a positive electrode or a reference electrode conventionally used for electrolytic reduction of a metal oxide. As a specific and non-limiting example, graphite or the like may be used as the anode, and W (pesudo) or the like may be used as the reference electrode, but it goes without saying that the present invention can not be limited by the anode or the reference electrode material.

4 is a process diagram showing a process of converting an alloy between a third metal and a second metal, which is a product of electrolytic reduction, into an alloy between a first metal and a second metal in the refining method according to an embodiment of the present invention .

(M3M2 (liquid) of Fig. 4) is produced by electrolytic reduction as in the example shown in Fig. 4, and then a metal oxide (a first metal ) May be added to convert the third metal and the second intermetallic alloy into an alloy between the first metal and the second metal. The reaction in which the third metal and the second intermetallic alloy are converted into the alloy between the first metal and the second metal may be a spontaneous reaction. This is because the metal belonging to the alkali metal and alkaline earth metal group has the strongest reducing power among the metals, the third metal reduces the metal oxide as a raw material, and an alloy (a liquid alloy) between the first metal and the second metal is produced, (The third metal) can be oxidized to the metal oxide.

In the switching step shown in Fig. 4, the temperature at which the switching process is performed may be performed at a temperature above the eutectic temperature of the second metal and the first metal. Specifically, the temperature at which the conversion step is performed may satisfy the following relational expression (2).

(Relational expression 2)

Te < Ta2 &lt; 1.5Tm &

In the relation 2, Ta2 is the temperature of step a2), Te 'is the eutectic temperature of the binary state of the first metal and the second metal, and Tm' is the melting temperature of the second metal. If the binary state diagram of the first metal and the second metal has more than two process points, then Te 'in the relationship (2) may be a relatively low temperature among the process temperatures of two or more process points.

As shown in relation 2, the temperature of the conversion step may be performed at a temperature exceeding the eutectic temperature of the binary state of the first metal and the second metal so that the conversion can be maintained while maintaining the liquid phase, Preferably, it is advantageous to perform at a temperature higher than the eutectic temperature of the eutectic point located closest to the second metal (pure second metal). Also, as shown in relation 2, the temperature of the conversion step can be performed at a temperature of 1.5Tm 'or lower based on the melting temperature (Tm', ° C) of the second metal. This is because there is a risk that conversion efficiency will decrease if the temperature of the conversion stage is excessively high. Thus, advantageously, the conversion step temperature can be 1.4 Tm 'or less, more advantageously 1.3 Tm' or less. As a practical example, according to an advantageous example, if the second metal is copper and the metal to be refined is zirconium, the advantageous temperature at which the conversion process of FIG. 4 is carried out may be between 1100 ° C and 1200 ° C.

As shown in FIG. 4, the electrode (cathode, anode, reference electrode, etc.) charged in the electrolytic reduction chamber during electrolytic reduction is removed as the process for converting the first metal to the second metal is based on the spontaneous reaction It is needless to say that the metal oxide which is a raw material may be put in the state, but the removal of the electrode may be selectively performed.

In the metal refining method according to an embodiment of the present invention, the metal oxide (oxide of the first metal) charged into the electrolyte of the electrolytic reduction tank in the conversion step of FIG. 4 may satisfy the following formula (1).

(Formula 1)

M _x O _y

In the formula (1), M is a first metal which is a metal to be reduced, x is a real number of 1 to 3, and y is a real number of 1 to 5.

As a specific example, the metal oxide may be at least one selected from the group consisting of zirconium oxide, hafnium oxide, titanium oxide, tungsten oxide, iron oxide, nickel oxide, zinc oxide, cobalt oxide, manganese oxide, chromium oxide, tantalum oxide, gallium oxide, Wherein the metal oxide is selected from the group consisting of oxides, lanthanum oxides, cerium oxides, praseodymium oxides, neodymium oxides, promethium oxides, samarium oxides, europium oxides, gadolinium oxides, terbium oxides, dysprosium oxides, holmium oxides, erbium oxides, thulium oxides, , Plutonium oxide, uranium oxide, neptunium oxide, plutonium oxide, amerium oxide, cerium oxide, berkelium oxide, caliperum oxide, euinitanium oxide, ferric oxide, mandelverium oxide, Two or more of them may be selected, but the present invention is not limited by the kind of the metal oxide. The metal oxide may be in the form of a powder, and may have an average particle size of 100 占 퐉 or less, specifically, 1 占 퐉 to 20 占 퐉, but is not limited thereto.

After the production of the alloy (liquid phase) between the third metal and the second metal by the above electrolytic reduction and the conversion into the alloy between the first metal and the second metal (liquid phase) are carried out, The solidification of the same alloy as the solidification of the alloy can be performed and the electrolytic refining similar to or similar to the electrolytic refining step described in the production method of the first aspect can be performed.

Hereinafter, zirconium is used as a target metal to provide an example of the actual metal refining according to the present invention, but the present invention is not limited to the embodiment shown.

(Example)

20 g of zirconium oxide (average particle size 4.5 탆) was used as a raw material, 30 g of copper was used as a negative electrode, and CaCl ₂ containing 5 wt% CaO was used as an electrolyte using an electrolytic reduction tank similar to that of Fig. 1 Graphite as the anode, and tungsten as the reference electrode. The reducing bath was heated to 1110 DEG C to melt the copper and the electrolyte of the negative electrode. The current density of the electrolytic reduction process was 500 mA / cm ^{2. The} anode potential was -1.3 to -1.5 V versus the tungsten reduction potential, and the electrolytic reduction process was performed for 0.9 hours, 1.6 hours, 3.3 hours, or 6.5 hours. After the electrolytic reduction process was completed, the solidified Zr-Cu alloy was slowly cooled at a rate of 15 ° C / min. Then, the remaining electrolyte was removed by heat treatment at 850 ° C in an argon gas atmosphere of 10 ^-3 torr.

The Zr-Cu alloy containing 3.2% by weight of zirconium (hereinafter referred to as 3% Zr-Cu alloy) was subjected to electrolytic reduction for 0.9 hours as a result of measurement of the content of Zr contained in the Zr- (Hereinafter referred to as 7% Zr-Cu alloy) containing 7.49% by weight of zirconium was produced when electrolytic reduction was performed for 1.6 hours, and it was confirmed that the Zr- (Hereinafter referred to as a 16% Zr-Cu alloy) containing 16.42% by weight of zirconium was produced when electrolytic reduction was performed during the electrolytic reduction for 6.5 hours, and 27.47% by weight Zr-Cu alloy containing zirconium (hereinafter referred to as 27% Zr-Cu alloy) was produced.

Oxygen concentration of the 3% Zr-Cu alloy was 142 ppm, the oxygen concentration of the 7% Zr-Cu alloy was 132 ppm, and the oxygen content of the 16% Zr-Cu alloy was measured using the ELTRA ONH2000 apparatus. It was confirmed that the oxygen concentration of all the alloys prepared with 223 ppm of oxygen concentration and 249 ppm of 27% Zr-Cu alloy was less than 300 ppm, and it was confirmed that alloys substantially free from oxygen were produced regardless of the electrolytic reduction process time .

6 is a scanning electron microscope (SEM) image of a structure of a 7% Zr-Cu alloy, and FIG. 7 is a scanning electron micrograph of a 16% Zr-Cu alloy FIG. 8 is a scanning electron microscope (SEM) image of the structure of the 27% Zr-Cu alloy. In the scanning electron microscope photographs of FIGS. 5 to 8, results of element analysis of an EDS (Energy Dispersive Spectrometer) of a spot indicated by a red dot are also shown. As can be seen from the EDS elemental analysis, in the scanning electron microscope photographs of FIGS. 5 to 8, it can be seen that the deep gray is Cu grain and the light gray is Cu-Zr intermetallic compound.

As can be seen from FIGS. 5 to 8, Cu-Zr intermetallic compounds are formed in the grain boundaries of copper, and when the content of zirconium in the alloy is 3 wt% or more, a continuum is formed around the copper grains. Further, when the content of zirconium in the alloy is 16 wt% or more, it can be confirmed that Cu-Zr intermetallic compound grains themselves are in contact with each other to produce a continuum of Cu-Zr intermetallic compound.

9 is a graph showing X-ray diffraction analysis results of a 7% Zr-Cu alloy (red graph in FIG. 9) and a 27% Zr-Cu alloy (black graph in FIG. 9). As can be seen from FIG. 9, an alloy composed of intermetallic compound phases of Cu-Zr (CuZr, Cu ₅ Zr ₁ , Cu _0.44 Zr _0.565 ) was produced together with copper.

Thereafter, a solidified Cu-Zr alloy (3% Zr-Cu alloy, 7% Zr-Cu alloy, 16% Zr-Cu alloy or 27% Zr-Cu alloy) , A LiF-KF eutectic salt containing 2.5 wt% of ZrF ₄ was used as an electrolyte, stainless steel was used as a cathode, and tungsten was used as a reference electrode. The electrolytic refining process temperature was 650 ° C and electrolytic refining was performed at a current density of 100 mA / cm ² for 10 hours.

Fig. 10 is a graph showing an optical photograph of each of a cathode and an anode (27% Zr-Cu alloy) after completion of electrolytic refining, electrolytic refining 2 hours and 10 hours after electrolytic refining, A scanning electron microscope photograph of a red region observed with a scanning electron microscope and an analysis result of an EDS element analysis of a red region.

As can be seen from FIG. 10, as the electrolytic refining progresses, it can be seen that pure Zr is electrodeposited and recovered to the cathode. As a result of measuring the mass of total Zr recovered through electrodeposition, the theoretically possible recovery amount (27% Zr-Cu Alloy) was recovered.

11 is a scanning electron microscope (SEM) image of a section of the anode after completion of electrolytic refining for 10 hours. As can be seen from FIG. 11, as the zirconium depletion region is formed from the surface to the center as the zirconium escapes, and the electrolytic refining progresses, the zirconium depletion region gradually progresses to the center of the anode. This means that continuum of the zirconium-copper alloy (zirconium-copper intermetallic compound) that provides a stable pathway of the zirconium in the center at the surface in the zirconium lean area continuously remains even if the zirconium escapes from the anode surface do. Zirconium The EDS elemental analysis of 10 arbitrary areas in the anode section of Fig. 11 revealed that the average zirconium content in the zirconium lean region was 2.1 wt% And the average zirconium content in the inner central region, which is relatively light gray, was 25.98 wt%. As a result, it can be seen that the minimum zirconium content in the solidified alloy for electrolytic refining of zirconium is 2.1 wt%. As a result of the electrolytic refining test using 3% Zr-Cu alloy, 7% Zr-Cu alloy or 16% Zr-Cu alloy, it was confirmed that the electrodeposition of zirconium was continued, similar to the result of 27% Zr- , It was confirmed that the content of zirconium in the surface region, which is a zirconium lean region, was 2.1 wt% within the error range. In order to experimentally confirm the effect of the zirconium migration route by the zirconium-copper intermetallic compound on electrolytic refining, the Zr-Cu alloy containing 1.2 wt% zirconium was obtained by controlling the process time of the electrolytic reduction process , And electrolytic refining tests were carried out in the same manner. 12 is a scanning electron microscope (SEM) image of a Zr-Cu alloy containing 1.2% by weight of zirconium. As shown in FIG. 12, the intermetallic compounds of zirconium-copper are not connected to each other, The electrolytic refining test showed that the Zr-Cu alloy containing 1.21% by weight of zirconium did not recover the zirconium by electrodeposition even during the electrolytic refining process for 10 hours Respectively.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Those skilled in the art will recognize that many modifications and variations are possible in light of the above teachings.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

Claims (12)

a) a third metal having a eutectic point with the first metal, which is a metal of the binary metal oxide, and a metal selected from the group consisting of one or more metals selected from the group consisting of alkaline metals and alkaline earth metals in binary states and eutectic point Preparing an alloy between the first metal and a second metal, which is a metal of the metal cathode, through electrolytic reduction using a solid metal cathode having a metal as the cathode; And
b) an electrolytic refining step of electrolytically refining the solidified alloy, and recovering the first metal from the alloy;
&Lt; / RTI &gt; The method according to claim 1,
The step a)
a1) electrolytically reducing an oxide of the third metal using an electrolyte containing an oxide of the third metal to produce a third metal and a second metal alloy in a liquid state; And
a2) introducing a metal oxide, which is an oxide of the first metal, into the electrolyte to convert an alloy between the third metal and the second metal to an alloy between the first metal and the second metal;
&Lt; / RTI &gt; 3. The method of claim 2,
Wherein the third metal and the second intermetallic alloy have a relatively higher density than the electrolyte. The method of claim 3,
Wherein the temperature of step a1) satisfies the following relational expression (1).
(Relational expression 1)
Te < Ta1 &amp;le; 1.8Tm
(In the relational expression 1, Ta1 is the temperature in the step a1), Te is the eutectic temperature in the binary state of the third metal and the second metal, and Tm is the melting temperature of the third metal) 3. The method of claim 2,
Wherein the temperature of step a2) satisfies the following relational expression (2).
(Relational expression 2)
Te &lt; Ta2 < 1.5Tm &
(Where Ta2 is the temperature of step a2), Te 'is the eutectic temperature of the first metal and the binary state of the second metal, and Tm' is the melting temperature of the second metal. The method according to claim 1,
Wherein the metal oxide satisfies the following formula (1).
(Formula 1)
M _x O _y
Wherein M is a first metal, a metal having a negative standard reduction potential with respect to a standard reduction potential of a second metal which is a metal of the metal cathode, x is a real number of 1 to 3, y is an integer of 1 to 5 It is a mistake) The method according to claim 1,
Wherein the metal oxide is selected from the group consisting of zirconium oxide, hafnium oxide, titanium oxide, tungsten oxide, iron oxide, nickel oxide, zinc oxide, cobalt oxide, manganese oxide, chromium oxide, tantalum oxide, gallium oxide, lead oxide, A rare earth element selected from the group consisting of lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, promethium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, One or more selected from oxides, uranium oxides, neptunium oxides, plutonium oxides, amerium oxides, cerium oxides, berkelium oxides, californium oxides, euinitanium oxides, ferric oxides, mandelverium oxides, &Lt; / RTI &gt; 3. The method of claim 2,
Wherein the oxide of the third metal is Li ₂ O, Na ₂ O, SrO, Cs ₂ O, K ₂ O, CaO, BaO or a mixture thereof. The method according to claim 1,
Wherein the electrolyte during electrolytic reduction comprises a molten salt of a halide of a metal selected from the group consisting of alkali metals and alkaline earth metals. The method according to claim 1,
Wherein solidification of the alloy between the first metal and the second metal is progressively cooled at a cooling rate of 20 DEG C / min or lower at a temperature of the liquid metal cathode at the time of electrolytic reduction to solidify. 11. The method according to any one of claims 1 to 10,
Wherein the alloy between the first metal and the second metal contains at least 2.1 wt% of the first metal. The method according to claim 1,
Wherein the metal cathode is copper.

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